Saturday, June 24, 2006

The science of decanting

According to the Oxford dictionary, “decanting” is an action of pouring a liquid from one container to another in order to separate the sediments from the liquid. For those of you who helped out in housework during the early 1970s, you may recall that one can buy homemade soya sauce in large bottle format. A delivery man would bring with him a cart filled with bottles of soya sauce for households who have ordered them. Each month, the used bottle would be exchanged for a fresh supply in another bottle. In any case, this soya sauce was so tasty that my mother would not buy from anyone else. The first time I performed decanting was on a bottle of homemade soya sauce. I would pour the content from its original bottle into another container, ever so carefully to ensure that as little sediment as possible was transferred over.

So, decanting is not just for wine. An aged wine which has been resting on its side would have collected a layer of sediments consisting of yeast cells, tannins, fining particles. Theoretically, the process of winemaking would have filtered such solids away before bottling. However, a small amount of particles that still went through the racking and ended up in the bottle. Over time as the wine ages in the bottle, such particles will collate to form a layer of solids along the inner surface of the bottle on which it lies. Indeed, there is absolutely nothing wrong to drink a wine that looks cloudy but sometimes it may not be so pleasant for some. Therefore, decanting is used to separate the sediments from the wine. A candle is often used to help in observing the flow of sediments, adding to the ceremony. In today’s high tech world, a white LED light (e.g a flexible reading light) is easier and clearer for this purpose, a twist to tradition.

For a young wine, decanting is believed to emulate an accelerated aging process by allowing oxygen to act on the phenolic compounds of the wine over a large surface area. We can decant a young wine either on a big bowled wine glass or a broad base decanter. The phenolic compounds in a young wine, especially those made in France and Italy, will benefit from decanting if it has to be drunk before maturation. Such compounds contribute to the pigments and tannins in the wine. The chemical structures of the tannins are polymers of different length. They are hydrolysable to form glucose and gallic or ellagic acids units. The catechin-gallate esters that are formed from gallic acid under the influence of oxygen are responsible for the dry taste in the mouth. They precipitate the proteins in our saliva while the wine pass through our lips. A young wine will benefit from decanting partly because of the action of oxygen in accelerating the release of aroma and flavor components from the wine. Therefore, it should be perfectly alright to leave the wine in the decanter or a wine glass for over 30 minutes before drinking. The young wine will become more approachable with time. On the other hand, an aged wine should be drunk as soon as it has been decanted. The reason being that an aged wine that is matured and ready to drink would have all its phenolic compounds assimilated in the wine. The act of introducing oxygen to the wine will remove the volatile aromatic components from the wine and if it is left unattended for more than 30 minutes, oxidation will kick in, creating an off-taste in the aged wine.

By Cher Lim
Wine Treasures Pte Ltd



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